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Thread: TTL/Analogue modulation - galvo?

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    Default TTL/Analogue modulation - galvo?

    Are there galvos that are TTL modulation galvos, and are there galvos that are analogue modulated galvos.

    Or this question is really a question for laser diodes. (ie is it a analogue modulation diode, or a ttl modulated diode)

    thx

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    By definition a galvo is an analog device.

    TTL means on or off; nothing in between. This applies to the laser's brightness. a TTL modulated laser is either on or off. That's it. An analog modulated laser can be anywhere from off to full on; like a light with a dimmer switch.

    James.

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    I think our friend may be a little mixed up - a galvo is a device used to position the beam a pair of them provide x & y movement to plot the coordinates for our vector art. In the good old days before the advanced technology we have now, galvos were used for blanking but I dont think its this type of blanking you are really asking about.
    I think you may mean a projector when you say galvo - is this correct?
    The last statement is on the right lines as yes, there are both analogue modulated and TTL modulated laser diodes (included in 'diodes' are DPSS here for simplicity). The diodes are configured to point at an XY pair of galvos and along with some other bits and bobs make up a projector

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    Actually the TTL/analog question doesn't apply to either the galvos or the LEDs, but to the LED driver circuit. A ttl driver either has the LED on or off. An analogue one has the LED at varying brightness levels in between. What you do with it after that (run it through x-y galvos, mirror bounce, liquid sky, etc.) is up to you.

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    Though a LED going through some galvo's are pretty pointless

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    Quote Originally Posted by Things View Post
    Though a LED going through some galvo's are pretty pointless
    SS lasers are LEDs. They are either directly responsible for making the light you see or they make IR that gets converted to the light you see. None the less they are LEDs.

    James.

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    James ... you know thats not true

    Laser light in its purest form is only emitted from the son of god

    so when we buy these so called laser DPSS heads... all they contain is pure "jesus juice" thats what emits the nice lights ...

    anyone wants some "jesus juice" i have pleanty to spare .... only $5000 a gallon .....











    ok its not nice to dis-respect the faith ... but hey ......... even jesus would laff

    but on a serious note....


    Miniaml ... the best thing to do is search though the forum here and find all the answers .... everyone here is willing to help you for futher info .... including me ...

    good luck in your search ..... all the best .... Karl

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    Quote Originally Posted by Banthai View Post
    James ... you know thats not true

    Laser light in its purest form is only emitted from the son of god

    so when we buy these so called laser DPSS heads... all they contain is pure "jesus juice" thats what emits the nice lights ...

    anyone wants some "jesus juice" i have pleanty to spare .... only $5000 a gallon .....
    LoL-. hehe nice one.

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    Quote Originally Posted by James Lehman View Post
    SS lasers are LEDs. They are either directly responsible for making the light you see or they make IR that gets converted to the light you see.
    James, I'm surprised! You know better.

    That is a gross oversimplification that really should be avoided. It raises all sorts of neophyte questions about "why can't I 'lase' the light from my LED" (sic) that we have had to answer many times before.

    Yes, laser diodes can emit light through spontaneous emission rather than stimulated emission (for example, when they are below lasing threshold but still have current flowing, or when the optical cavity has been damaged by excessive current).

    However, that fact alone does not make them LEDs in the classical sense. The structure is different, the doping is different, the connections are different, and their operation is completely different. Calling them LEDs is misleading at best.

    There are fundamental differences between an LED and a laser diode, and one is not equal to the other.

    Adam

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    you just route the TTL signal right to the galvo input, or maybe level shift it and offset it with a simple opamp circuit first. there is flag blanking, figure four blanking (uses 2 mirrors plus a mirror on the galvo to eliminate "tails") and linear blanking (difficult at first) where the galvo obstructs a beam at a lens focal point, then the beam is recollimated by a identical lens (also known as telescope blanking). you can also use a galvo after a prism for color selectiion, or split a argon into blue and green with dichros, recombine them with more dichros, modulate them with galvos, then recombine them. been there, done that. ttl flips between less then .6 volts and then highe rthen 2.4 volts by definition. this is enough to move the galvo in and out of your average beam
    you can also make a small retroreflector and glue it on the galvo shaft, and there are even more variations I wont get into


    acousto optic devices such as aoms and pcoams make it much easier.
    even for dpss.

    does that answer the question?

    STeve

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